The market for air purifiers is growing as we become more conscious of breathing air that is free of airborne virus particles as well as such things as dust, pollen, mould, bacteria and pollution.
But is highly cleansed air really the healthiest thing we can inhale? Researchers at Flinders University don’t think so. They argue that although reducing exposure to pollutants is important, we also need to develop strategies to ensure we are exposed to the “good bugs” in the air.
Microbial ecologist Jake Robinson says there is a strong argument for rewilding at least some of the roughly 11,000 litres of the air we breathe daily and making sure we encounter microbes that are good for our health.
“Bioaerosol research has been around for decades,” he says, “but it’s mostly been focused on things that harm agriculture or human health. There have been missed opportunities to look at organisms in the air that are probably having a beneficial effect on our immune system.
“Ever since germ theory in the late 19th century, we’ve been demonising microbes, but most are actually either harmless or fundamental to our survival and that of the plants and animals around us.”
Robinson isn’t arguing against hygiene practices to prevent disease. Rather, he is saying filling our lungs with natural, unpolluted outdoor air filled with a diverse balance of bioaerosols, including fungi, pollen and bacteria, is good for us.
“We don’t 100% know what healthy air is, but we do think it contains lots of different types of species,” he says.
Some of the microbes we are exposed to are “invisible friends” that we co-evolved with and that help regulate our immune system.
“The idea is that we need to be exposed to as many different species of microbes as possible from a young age because they train our immune system so it can mount a much more efficient response to pathogens in the future,” says Robinson.
Without proper regulation by these microbes, the immune system will attack things it shouldn’t, such as dust and pollen, or even our own cells, as in autoimmune disorders.
Healthy soils feed the air with diverse microbes. One 2022 study in Finland inoculated playground sand in daycare centres with a biodiversity powder that included commercial soil, leaf litter, peat and sphagnum moss. Researchers found daily exposure to this higher microbial diversity resulted in positive differences in immune response in children who were aged three to five.
In an earlier study, scientists from the Natural Resources Institute in Finland transformed the playgrounds of daycare centres with forest-floor materials, greening the asphalt and gravel with moss, shrubs, grasses and green sod. Blood tests showed the children who played there developed a higher ratio of inflammation-dampening molecules to pro-inflammatory ones, suggesting their immune systems were engaging with the bugs they were touching and breathing.
The concept of the aerobiome – the microbiome of the air – is relatively new and there are likely to be more benefits to breathing natural air. There is no shortage of research about the harms polluted air can cause, however. Long-term exposure has been linked to everything from decreased sperm motility to respiratory illness, stroke and cardiovascular disease and even a greater risk of dementia, according to a recent Harvard University study.
Superfine particles of pollution, mostly released by cars and industry, enter not only the lungs but also the bloodstream, damaging cells over time. The World Health Organisation claims 99% of the global population breathes air with levels of pollutants that exceed its guideline limits and has estimated this kills about seven million people a year.
Tackling the sources of pollution is a priority, but restoring ecosystems and the complexity of vegetation to a more natural state will also play a part in creating healthier air and humans. In the meantime, says Robinson, we should be spending as much time outdoors in nature as possible, breathing deeply and bathing in microbes.
“Microbes are everywhere and trying to get rid of them is futile,” he says. “Rather than trying to live in sterile environments, we should be trying to restore the natural environments around us.”
